1. Field of the Invention
The present invention relates to a seat occupant detection system of a vehicle that is used in a passenger protection system.
2. Description of the Related Art
JP-A-11-271463 discloses an electrostatic seat occupant detection system that employs a capacitance sensor and a passenger detecting ECU. The capacitance sensor provides an output signal as an amount of current or a level of voltage when an electric field between a main electrode and a vehicle body changes.
However, such an occupant detection system may not operate accurately if a seat of a vehicle gets wet with water because the state of the electric field is considerably affected by water.
JP-A-2006-27591 or its counterpart US 2005/0275202 A1 discloses another occupant detection system that warns a driver of an abnormality and carries out an abnormality process when a seat gets wet. However, it is not possible for this system to accurately detect a seat occupant if a seat of a vehicle gets wet.